This invention relates to a master frame assembly for use with a screen printing apparatus and, more particularly, to a master frame assembly having a sealed chamber for containing an ink solvent for the ink being applied through a printing screen to an underlying substrate.
The present invention relates to a screen printing apparatus which uses a master frame or chase to which are releasably clamped screen printing frames having a screen on which is deposited ink which is forced through screen by a squeegee and flood bar assembly. The present invention is also directed to providing such screen printing apparatus with a new and improved sealed chambers or solvent guard system over that which is disclosed in U.S. Pat. No. 4,545,300 and in pending patent application Ser. No. 723,930 filed Apr. 16, 1985, entitled "Screen Printing Assembly".
The sealed chamber or solvent guard system contains the ink solvent against escape to the ambient atmosphere. Loss of solvent vapor from the ink dries the ink and contaminates the ambient atmosphere particularly in a confined and enclosed room. Better printing may be achieved by containing the solvent within a sealed chamber. However, the sealed chamber should not interfer with the usual reciprocating movement of the squeegee assembly relative to the printing screen or the usual adjustments of the squeegee and flood bars from a convenient location external to the master chase and screen frame carried thereby.
U.S. Pat. No. 4,545,300 discloses a support frame which is used in lieu of the usual master frame or chase with the support frame having a movable, upper flexible cover sheet attached to and movable with a squeegee and flood bar mechanism. This movable upper cover sheet is sealed to the support frame to define therewith the upper part of the sealed chamber. The adjustment controls for the squeegee and flood bar are positioned above the flexible sheet which is attached centrally thereof to the squeegee mechanism and which has its opposite ends attached to winding spools or reels for the cover sheet. The support frame disclosed in U.S. Pat. No. 4,545,300 has a considerable depth in order to mount the cover sheet, reels and the seals. Unlike the frame or chase which can releasably support various widths of screen frames used by the screen printer, the support frame is sized for only one size of screen printing frame. Thus, the sealed chamber illustrated in U.S. Pat. No. 4,545,300 is included in a specially constructed support frame which needs to be substituted for the conventional master frame or chase.
The present invention is directed to a master frame or chase assembly which has been adapted to provide a sealed chamber and which can provide a sealed chamber with several different widths or lengths of screen frames so that it can be used in the manner of the conventional master chase while providing the sealed chamber to contain the solvent vapors. The preferred form of the present invention seals the flexible sheet directly to a screen frame thereby eliminating the depth of frame needed in order to obtain the sealed chamber shown in the aforesaid patent. With the preferred embodiment of the invention, sealing pads or members on the master chase are capable of sealing with several different widths of screen frames which may be mounted in the master frame. The unique construction of the invention allows a reduction in the number of parts needed to form the sealed chamber and provides an economical commercially feasible sealed chamber for otherwise conventional screen printing presses. The invention allows the retrofitting of existing screen printing machines, particularly of the type having a master frame, with a sealed solvent holding chamber cooperating with the screen frame.
Accordingly an object of the present invention is to provide a new and improved master frame assembly having a sealed chamber for solvent vapors.